In general, in the development of new motor vehicles and the further development of existing motor vehicles, especially utility vehicles, it is attempted to reduce fuel consumption and the emissions of harmful substances and CO2. Besides the technical optimization of motor vehicles such as the development of low-consumption and low-emission drive engines, efficiency-optimized multi-stage change-speed transmissions, tires with low rolling resistance and aerodynamic car bodies, driver cabins and superstructures of trucks, a further possibility for reducing fuel consumption and the emissions of harmful substances and CO2 relates to suitable driving operation control during the use of the motor vehicle.
To save energy and costs and to reduce environmental pollution, in appropriate driving situations a vehicle can continue to move ahead in a temporary rolling or freewheel mode with no propulsive drive. In particular, in a motor vehicle in the rolling mode the combustion engine can be operated in an idling mode in which the consumption and emissions are as low as possible while the vehicle is rolling with its drive-train open. If in such a driving situation the combustion engine is switched off in order to increase the saving effect even more, the vehicle moves in a so-termed freewheel mode. These functions are already known.
Depending on the drive-train components present and the design of the transmission, the force flow interruption can take place by shifting the transmission to neutral or by opening a starting clutch as soon as rolling or freewheeling becomes possible.
From DE 10 2009 028 242 A1 a method for controlling a rolling or freewheeling mode of a vehicle is already known. To enable as effective as possible, yet comfortable and reliable driving operation, a force flow interruption in the drive-train is permitted when the counter condition of a rolling or freewheeling mode counter is below a specified first threshold value or assumes the value zero, such that the rolling or freewheeling counter is incremented if at least one event stored in a event table occurs and otherwise the counter is decremented or kept the same. By virtue of the method according to DE 10 2009 028 242 A1 the driving condition of the vehicle and the topography that influences the vehicle are correctly interpreted in such manner that unnecessary shifts to neutral, i.e. neutral shifts that have no saving effect or which activate the rolling or freewheeling mode in situations when that is unwanted by the driver, or which are possibly safety-relevant, can be reliably avoided.